Dicarboxylic acids as pH sensors for hyperpolarized 13C magnetic resonance spectroscopic imagingElectronic supplementary information (ESI) available: Full experimental details, details on chemical synthesis, and molecular characterization. See DOI: 10.1039/c7an00076f

Imaging tumoral pH may help to characterize aggressiveness, metastasis, and therapeutic response. We report the development of hyperpolarized [2- 13 C,D 10 ]diethylmalonic acid, which exhibits a large pH-dependent 13 C chemical shift over the physiological range. We demonstrate that co-polarization with [1- 13 C,D 9 ] tert -butanol accurately measures pH via 13 C NMR and magnetic resonance spectroscopic imaging in phantoms. Hyperpolarized [2- 13 C,D 10 ]diethylmalonic acid demonstrates long-lived signal enhancements for high-accuracy pH imaging via 13 C MR spectroscopic imaging.